MarkD

where would the "remaining energy" hide that would activate the airbag?

On the main thread topic:
Please note that the problem described in Streather's book is not the one originally mentioned in this thread above (unless I misunderstood).
From what I can tell there are two different failure types:
1. lighting issues (mentioned in book)
2. Psychotic display, glitches various segments, tap gauge and it goes away for a while.

Is that correct or I am reading these posts incorrectly? Or are we describing the same issue?
Mine freaks out and display partial segments on the display.

I've serached here and on the 993tt forum and found that the lighting issue can be repaired. I haven't seen an answer to #2 aside from replacement at about $1K USD

Caveman

Bill - thanks of the info.

Mark - Most of us seem to have the intermittent lighting issue judging by the posts I have seen on this forum. What was the fix that came up on the TT forum?

Cheers,

David

MarkD

David,
So, it's just me and the poor guy in post #3 of this thread with the oddball problem?

Here is the "fix" I ran accross on the 993tt forum: https://rennlist.com/forums/showthre...ferrerid=35947
He tried the transistor repair which failed and then performed more of a workaround to put power to the light. Neat trick and simple. Read carefully, he didn't have any pics.
If you cannot do this yourself any guage shop like some mentioned here could do this for you. Personally, I would want mine wired to come on when the key is in accessory position since I typically don't drive with my headlights on.

Then again, I don't have this problem. I almost wish I did...

Caveman

Mark,

Sadly I think it is just you two. Someone else has done the wire it up fix. I would agree with you that it would make more sense to have a simple on/off link to when the car's accessory circuit is powered-up.

Cheers,

David

C4 NLW

Hey Billa77,

Thanks for thhe response. I have the same problem as mentioned by Mark. My display becomes erratic with different segments of the display lighting up in a random pattern. I tap the guage and the figures return. Would the fix for this involve the same Diode 1N4118 or would be it be the transistor BS170 - or something else?

Caveman

I hate to say it but that sounds like a display issue; i.e. the led/lcd unit itself. :-(

MarkD

or a loose solder joint.
mine hasn't done it for a while now. it will be hard to track down.
it would be easier if it was the display module itself

bill964

I've just repaired my OBC by replacing the BS170 Transistor with a 2N7000. It has to be soldered in reverse to the BS170 only because the pins are reverse on this type. My backlight was competely out and now working fine. The Transistor cost me 0.85c here in Australia. Hope this helps other members.

Caveman

Thanks Bill,

How tricky was it do if you were a bit ham-fisted with only limited soldering practice?

Cheers,

David

bill964

David,

You need a fine tipped soldering iron, about 1/16" and temperature controllable. The circuit board solder pads are very small and you'll damage it with too much heat. I'll try and get a picture up soon.

Regards,

Bill

bill964

OBC backlight repair

Here's a picture of the replacement 2N7000 transistor fitted to the main circuit board. The original BS170 face the opposite way toward the eight pins. Only the outside legs of the transistor are reversed.

Cheers,
Bill

cowtown

Very nice. I hope you consider posting that picture in the DIY area with a few sentences on the repair!

Caveman

Nice job! Thanks for the photo. How easily do you think you could explain to an electronics shop what you wanted replaced and with what?

Cheers,

David

bill964

David,

Once you remove the Tacho, do the following:
1. Remove a couple of small screws on the rear of the Tacho.
2. Carefully wriggle the rear section of the Tacho apart. This is joined by a couple of sets of pins and sockets (the sockets are shown on the photo next to the Transistor)
3. The removed rear section contains the circuit board.
4. Remove two or three small screws on this board to remove the board from the rear housing.
5. Then as shown in the Photo have the Transistor replaced. It's a very sensitive Transistor so whoever does the job has to be carefull with Static electricity and the amount of heat used.
6. Reassemble in the reverse and enjoy.

Hope it works for you!

Regards,

Bill

Caveman

Thanks Bill,

Kind of scary but I might see if I can get someone to do it.

Cheers,

David